Compositions and methods for composite fuels

ABSTRACT

A solid composite fuel for the mitigation of emissions from a coal-fired power plant includes a solid monothilic fuel material formed from the pyrolysis of a coal material and at least one solid renewable fuel material.

BACKGROUND OF THE INVENTION

The present invention relates generally to composite fuels, and more particularly, to compositions of fossil fuels and methods of producing the same.

The world is facing an energy deficit of unprecedented proportions. Within the next two decades energy demands from outside the United States will exceed the United States' energy consumption by 32 times. This well recognized threat will bring tremendous pressure on the price of imported energy resources and peril to our economy and security.

The use of fossil fuels continues to increase at about the growth rate of emerging economies because fossil fuels are available and provide a low cost path to provide the energy necessary to fuel economic growth. Burning fossil fuels continues to add emissions to the atmosphere at an ever-increasing rate, increasing the risk that the atmosphere may reach a “tipping point” at some as-yet unknown concentration, resulting in irreversible climate change. For example, coal is favored for its low cost, but depending on its water content coal produces emissions, for example between 1.4 and 2.8 tons of carbon dioxide (CO₂) for each ton of coal burned, about 50% more than burning natural gas. For at least this reason, substantial research has been undertaken with the intent to eventually implement carbon capture and sequestration, (CCS) or “clean coal” technologies which, to date, remain largely theoretical. A 2008 study by MIT entitled “The Future of Coal” concludes that CCS will likely double the capital and operating cost of a utility scale coal-fired power plant and the pass along capital and operating costs of retrofitting existing power plants will likely double the cost of electricity, further stifling global economic growth. The situation is worsened by the fact that CCS has yet to be demonstrated on a commercial scale and proven to be safe. Efforts to demonstrate CCS technology have failed several times suggesting that it will be many years before CCS can be implemented, if ever. Clearly, it would be more expedient and safer to simply substitute renewable fuel for coal, if it could be implemented at utility scale and within the current regulatory framework.

Typically, in some known fossil-fueled power plants, coal is burned to produce energy. However, coal produces emissions that include carbon dioxide and water vapor, as well as other substances including nitrogen, nitrogen oxides, sulfur oxides, and fly ash and mercury. As such, the power plants may use renewable fuels to reduce the amount of emissions.

At least some known power plants co-fire with renewable fuels, including biomass or biomass char (Bio-char). Other renewable fuel materials, for example, materials that have been tested as fuel in specially constructed power generating plants, include terrestrial plant materials, aquatic plants including algae and micro algae, various forms of urban waste streams including paper, wood, shredded tires, plastics, dried sewage sludge, etc. However, the variability of the properties of these renewable fuel streams greatly complicates the operations of the power plant for a number of reasons including the variability in moisture content, fixed carbon content, carbon to hydrogen ratio, halogen contamination, ash type and content, sulfur type and content all of which impact the control of the ratio of coal to renewable fuel. In addition, typical coal fired power plants are not equipped to handle such variability in the fuel stream or the induced variability in the combustion process which may damage power plant components including fire box structures, burners, boiler tubes and turbines. Variability in combustion waste products also causes operational problems including fouling of boiler tubes and difficulty in meeting regulatory mandates for tail gas cleanup including sulfur oxides, nitrogen oxides, mercury and ash mitigation.

In addition, renewable fuels, including biomass, are difficult to obtain in a large quantity with a reliable supply of a uniform material. Biomass from agricultural waste varies in moisture and ash content and may contain contaminates including non-combustible materials including metal debris, glass, and dirt, as well as biological contamination of unwanted species, micro organisms and fungus, and wild animal carcasses. Other key parameters including ash and sulfur content are species specific, so that co-firing with random species of feed material is problematic. Cultivated biomass or agricultural waste from a single species, including Bagase from sugar cane or cultivated biomass including miscanthus, switch grass or micro-algae mitigates these problems to a large degree, providing industrial quantities of a more uniform feed material for fuel production, but still containing excessive amounts of moisture resulting in reduced heating value. If located near or co-located with a power plant these could reasonably be used to mitigate CO₂ by co-firing with conventional fossil fuels, for example coal, if the quality of the biomass, especially moisture content and fixed carbon content, were made uniform in large quantities, on the order of hundreds of tons per day, and over long operating periods, on the order of years. Co-firing a power plant with biomass, without addressing these issues, results in a marked decrease in power plant reliability, a de-rating of the power plant and a permanent increase in capital and operating costs.

At least some known development is directed toward power plant use of micro algae as a co-firing fuel with one significant problem being the cultivation of micro algae. Micro algae are the fastest growing plants on the planet, able to absorb CO₂ at high rates while doubling their mass in as little as 8 hours, typically yielding about 20-40% of their weight in lipid oils which can be readily converted into transportation fuels including bio-diesel, synthetic gasoline and bio-jet fuels. Many researchers, governments and companies are investigating the growing process, oil extraction processes and promoting the use of these oils as alternative fuels. The balance of the algae weight, “spent algae”, is rich in proteins, sugars, cellulose and related materials. It has been demonstrated that these may also be converted into liquid transportation fuels through fermentation, treatment with enzymes, etc., generally resulting in alcohols, or dried and used a cattle feed or fertilizers. These potential routes for disposing of the spent algae have yet to be demonstrated at commercial scale with the largest algae production facilities in the world only 1/20^(th) the size needed to mitigate ½ of the CO₂ from an average sized power plant of 500 MW capacity. There are also other significant challenges beyond just cultivating enough biomass. Economically extracting oil from algae at power plant scale is, as yet, unsolved, as is byproduct processing and disposal of quantities of thousands of tons per day, a rate on-par with the mass of power plant fuel. Therefore utility-scale algae production is not presently practiced and energy production from other renewable sources, including cultivated biomass, usually from forest products, and use of post consumer or industrial waste as renewable fuel is extremely limited in scope due to the scale and complexity of the enterprise.

The process of pyrolysis has been practiced for over 5,000 years to enhance the fuel properties of biomass, usually in the manufacture of charcoal from wood. Pyrolysis has also been demonstrated for the use of upgrading the fuel properties of coal by reducing moisture and increasing fixed carbon as reported by Jones, J. F. et al. “Char Oil Energy Development, Final Report”, September, 1975, and the ENCOAL project Final Report, DOE/MC/27339-5798 (DE98002007). However, pyrolysis has not been demonstrated to produce fuels with renewable content suitable for use as a power plant fuel at utility scale.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a solid composite fuel for the mitigation of emissions from a coal-fired power plant is provided. The solid composite fuel includes a solid monolithic fuel material formed from the pyrolysis of a coal material and at least one solid renewable fuel material.

In another aspect, a solid composite fuel for the mitigation of emissions from a coal-fired power plant includes a coal material, at least one solid renewable fuel material and at least one binder. The at least one binder is added to the coal material and the at least one solid renewable fuel material.

In a further aspect, a method of making a solid composite fuel is provided. The method includes preparing a coal material and at least one solid renewable fuel material. The coal material and the at least one solid renewable fuel material are blended into a mixture and dried. The mixture is pyrolized in at least one pyrolizer. Resulting solid chars are cooled to form a solid composite fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow chart illustrating a method for producing a two component carbon mitigating fuel.

FIG. 2 is a schematic flow chart illustrating an alternative method for producing a two component carbon mitigating fuel.

FIG. 3 is a schematic flow chart illustrating a method of producing a three component carbon mitigating fuel.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments described herein relate to a synthetic fuel material for the mitigation of emissions from fossil-fueled power plants, and the process for making the same. The fuel material provides an alternative fuel for combustion that is a monolithic composite char product resulting from pyrolysis of an amalgamation of coal and a renewable fuel material. The renewable fuel material is derived from biomass or post consumer waste, ligneous materials, plastics and the like. Replacement of coal in a coal-fired power plant with this composite fuel displaces some of the coal normally burned with renewable fuel thereby effectively mitigating emissions. Emissions include, for example, CO₂ emissions. In one embodiment the composite fuel also has substantially reduced levels of sulfur and mercury. This improves the power plant's generating efficiency thereby further reducing emissions as well.

The embodiments described herein provide for a specific set of feed materials and preparation processes which function to create a monolithic structure during or subsequent to pyrolysis. This results in a fuel product which can be transparently substituted for all or part of the feed coal in coal-fired power plants. In one embodiment, mitigation of at least 10%, and in another embodiment mitigation of at least 15%, of CO₂ emissions from fossil-fueled electric power generating plants is possible. In yet another embodiment, up to 50% mitigation of CO₂ emissions is possible. This mitigation occurs without any modification of the electric power generating plant, its controls or its operations.

The embodiments described herein further provide for a compounded monolithic composite fuel product for utility power plants. This results in reduced CO₂ emissions, without stack gas cleanup and without any modification of power plant equipment or changing the power plant combustion process or its controls. This fuel is of a composition that delivers a specified amount of CO₂ mitigation while also controlling regulated emissions of sulfur and mercury to their required levels. The product and its process of manufacture are described below.

A new and novel monolithic fuel product is described. The fuel exhibits controlled physical, chemical and combustion properties including emissions profile and including in its content a renewable fuel for the purpose of CO₂ mitigation. The fuel which can be transparently substituted for coal in a coal-fired power plant is described.

FIG. 1 is a schematic flow chart of an exemplary method for producing a two component carbon mitigating fuel. In the exemplary embodiment, a coal material 102 and at least one solid renewable fuel material 104 are selected. Coal material 102 includes, for example, coal from at least one of anthracite, bituminous, sub-bituminous or lignite, including coal fines and waste coal materials derived from the classes of coal. Solid renewable fuel material 104 includes, for example, fuels including biomass, woody biomass, grasses or any other terrestrial plant materials, including any combinations thereof. In one embodiment, solid renewable fuel material 104 includes aquatic plants, for example, algae and micro algae, including diatoms. In another embodiment, solid renewable fuel material 104 includes solid carbon-containing waste, including industrial and municipal waste, post consumer and post industrial wastes. In another embodiment, solid renewable fuel material 104 includes wood and paper, including coated paper waste, polymer waste containing essentially no halogen containing polymer, and any combinations thereof. In yet another embodiment, solid renewable fuel material 104 includes material from dry sewage sludge containing less than 10% ash.

In one embodiment, solid renewable fuel material 104 includes terrestrial plant materials that are ligneous materials including wood, for example, forest biomass or wood waste, or cane, including miscanthus, or grasses, for example, switch grass, sugar cane or Bagase from sugar cane processing or from agricultural waste, including corn or wheat straw. Other ligneous waste materials include particle board, fiber board, chip board, paper board, paper, coated paper and the like.

In another embodiment, solid renewable fuel material 104 includes algae, either whole or spent algae, including micro-algae (after the oil has been pressed or extracted from the algae) or diatoms, either whole or spent diatoms (after the oil had been pressed or extracted from the diatoms).

In one embodiment, solid renewable fuel material 104 includes one or more synthetic materials including plastics, for example, plastics that contain less than 1% halogen containing polymers, therefore excluding Teflon, Kynar, PVC and the like. Applicable synthetic materials include acrylic, polycarbonate, polyethylene, polypropylene, polyethylene teraphthalate (PET), polybutylene teraphthalate (PBT), phenolics, polysulfone and polyethersulfone, and similar materials that may include fillers, for example, mineral fillers or glass fiber fillers. In one embodiment, the materials are in concentrations of less than 10% by weight.

In one embodiment, solid renewable fuel material includes petroleum coke.

In the exemplary embodiment, coal material 102 is directed to and prepared in material preparation unit 106 and solid renewable fuel material 104 is directed to and prepared in material preparation unit 108. Material preparation units 106 and 108 include sizing, analyzing, quantifying and measuring the properties of coal material 102 and the solid renewable fuel material 104. Coal material 102 is then directed to metering control unit 110 and solid renewable fuel material 104 is directed to metering control unit 112 where metering control units 110 and 112 feed materials at a rate determined by the moisture and carbon content of feed materials 102 and 104 as measured by material preparation units 106 and 108 respectively, so as to obtain the specified ratio of coal and renewable solid fuel material in the desired composite fuel product 136.

In the exemplary embodiment, coal material 102 and solid renewable fuel material 104 are blended in dry blending unit 114 to form a mixture. For example, coal material 102 and solid renewable fuel material 104 are mixed sufficiently to produce an essentially uniform mixture of like-sized particles of coal material 102 and solid renewable fuel material 104. The mixture is then directed to a dryer 116 and dried at a temperature between 212° F. and 300° F. During drying in dryer 116, water is recovered from the mixture in water recovery unit 118. In one embodiment, coal material 102 is greater than 20% by weight of the dry weight of the mixture, and in another embodiment greater than 50% by weight of the dry weight of the mixture. The mixture is then directed to a first pyrolizer 120 and pyrolized. During pyrolization in first pyrolizer 120, the temperature of the mixture is raised, for example, to about 350° F. and mercury is recovered from the mixture in mercury recovery unit 122. In the exemplary embodiment, the mixture is then directed to a second pyrolizer 124 and pyrolized. During pyrolization in second pyrolizer 124, the temperature of the mixture is raised, for example, to between 800° F. and 1200° F. and oils are recovered in oil recovery unit 126 as oil product 128. Oil product 128 includes tar oil. In one embodiment oil product 128 is used directly as fuel. In another embodiment oil product 128 is further processed into other products by hydrocracking, hydrotreating, distillation and other processes known to those skilled in the art to form synthetic crude oil and chemicals.

In the exemplary embodiment, a resulting solid char is produced after cooling the mixture in cooling and stabilization unit 130. The resulting char may be formed into pellets, rods or briquettes in unit 132 with the addition of at least one binder material 134. Binder material 134 includes, for example, at least one of sugar syrup and starch materials, materials of unsaturated, oxygenated and cyclic hydrocarbons, including phenolics and any combinations thereof. In an exemplary embodiment, a portion of tar oil product 128 recovered in oil recovery unit 126 is substituted for all or part of binder material 134. In one embodiment, the binder includes components of the recovered tar oil product 128 with an initial boiling point in excess of 500° F. In another embodiment, the binder includes components of the recovered tar oil product 128 with an initial boiling point in excess of 600° F., including substantial amounts of waxy and/or phenolic compounds. In another embodiment, binder material 134 includes components of the recovered tar oil product 128 which are substantially insoluble in C₁₀ or lower alkane solvents at temperatures of less than 250° F.

In the exemplary embodiment, a composite solid fuel 136 is provided and identifiable in that the individual pyrolized coal macerals are clearly identifiable in a matrix of the composite solid fuel 136. In one embodiment, composite solid fuel 136 is a solid composite non-agglomerating synthetic fuel. In another embodiment, composite solid fuel 136 is a monolithic fuel material that is essentially inseparable from coal fuel material 102, while at the same time coal fuel material 102 remains detectable, for use as a solid fuel in coal-fired plants.

In one embodiment, solid composite fuel 136 is a solid monolithic fuel material formed from the solid pyrolysis products of coal material 102 and solid renewable fuel material 104. In another embodiment, binder material 134 is added to coal material 102 and solid renewable fuel material 104 and formed into a solid shape prior to pyrolysis resulting in a solid monolithic fuel product.

In one embodiment, coal material 102 and solid renewable fuel material 104 are blended into a mixture which may be dried or may be mixed with binder material 134, formed into a solid shape and then dried. The mixture or solid shape is pyrolized in a first pyrolizer and then pyrolized in a second pyrolizer. Resulting solid chars or solid char shapes are cooled to form solid composite fuel 136.

Composite solid fuel 136 exhibits consistent and repeatable properties as a result of its exposure to pyrolizing temperatures, including a very low equilibrium moisture content, a precisely controlled volatile content, reduced ash content, a significantly reduced sulfur content, a high fixed carbon content, an improved carbon to hydrogen ratio, a mid-range Hardgrove Grindability Index, and an improved Gross Calorific Value, (GCV) properties including those listed in reference to the exemplary embodiment shown in FIG. 1.

In one embodiment, composite solid fuel 136 exhibits an equilibrium moisture content between 0% and 10%. In another embodiment, the equilibrium moisture content is between 0% and 5%. In yet another embodiment, the equilibrium moisture content is between 0% and 2%.

In one embodiment, composite solid fuel 136 exhibits a volatile content between 10% and 30% on a Dry Ash Free (DAF) basis. In another embodiment, the volatile content is between 10% and 22% on a DAF basis. In yet another embodiment, the volatile content is between 14% and 22% on a DAF basis.

In one embodiment, composite solid fuel 136 exhibits an ash content between 0% and 10%. In another embodiment, the ash content is between 0% and 5%.

In one embodiment, composite solid fuel 136 exhibits a sulfur content between 0% and 10%. In another embodiment, the sulfur content is between 0% and 5%. In yet another embodiment, the sulfur content is between 0% and 3%. In still another embodiment, the sulfur content is less than 1%.

In one embodiment, composite solid fuel 136 exhibits a fixed carbon content greater than 98%. In another embodiment, the fixed carbon content is between 86% and 98%. In yet another embodiment, the fixed carbon content is between 69% and 86%. In still another embodiment, the fixed carbon content is greater than 69%, or greater than 89%.

In one embodiment, composite solid fuel 136 exhibits a carbon to hydrogen ratio of composite solid fuel between 10 and 30 on a DAF basis. In another embodiment, the carbon to hydrogen ratio is between 10 and 20 on a DAF basis. In yet another embodiment, the carbon to hydrogen ratio is between 15 and 25 on a DAF basis.

In one embodiment, composite solid fuel 136 exhibits a Hardgrove Grindability Index between 30 and 120. In another embodiment, the Hardgrove Grindability Index is between 40 and 100. In yet another embodiment, the Hardgrove Grindability Index is between 80 and 100.

In one embodiment, composite solid fuel 136 exhibits a GCV greater than 10,500 btu/lb. In another embodiment, the GCV is greater than 11,500 btu/lb. In yet another embodiment, the GCV is greater than 12,500 btu/lb.

In one embodiment, composite solid fuel 136 contains greater than 10% solid pyrolysis product from a renewable fuel material, and in another embodiment greater than 20% solid pyrolysis product from a renewable fuel material, and in yet another embodiment greater than 45% solid pyrolysis product from a renewable fuel material.

In one embodiment, composite solid fuel 136 produces sulfur emissions of less than 1.5 pounds of SO₂ per million BTU.

FIG. 2 is a schematic flow chart of an alternative exemplary method for producing a two component carbon mitigating fuel. In this embodiment, a coal material 202 and at least one solid renewable fuel material 204 are selected. Coal material 202 and solid renewable fuel material 204 include, for example, materials including those listed in reference to the exemplary embodiment shown in FIG. 1. Coal material 202 is directed to and prepared in material preparation unit 206 and solid renewable fuel material 204 is directed to and prepared in material preparation unit 208. Material preparation units 206 and 208 include sizing, analyzing, quantifying and measuring the properties of coal material 202 and solid renewable fuel material 204. Coal material 202 is then directed to metering control unit 210 and solid renewable fuel material 204 is directed to metering control unit 212 where metering control units 210 and 212 feed materials at a rate determined by the moisture and carbon content of feed materials 202 and 204 as measured by material preparation units 206 and 208 respectively, so as to obtain the specified ratio of coal and renewable solid fuel material in the desired composite fuel product 236.

In the alternative embodiment, coal material 202 and solid renewable fuel material 204 are blended in dry blending unit 214 to form a mixture. For example, coal material 202 and solid renewable fuel material 204 are mixed sufficiently to produce an essentially uniform mixture of like-sized particles of coal material 202 and renewable solid fuel material 204. The mixture is then directed to mix and pelletize unit 216 which uses heat and pressure to form the mixture into pellets, rods or briquettes. In one embodiment, at least one binder material 218 is added to the mixture to strengthen the subsequent product.

In one embodiment, coal material 202 and solid renewable fuel material 204 are mixed with binder material 218, at a sufficiently high sheer rate to further reduce their particle size and produce an essentially homologous amalgam, which is subsequently extruded, or rolled into pellets or rods. In one embodiment, the pellets or rods are formed by extruding the amalgam through a circular orifice and are cut or broken into pre-determined lengths. In another embodiment, the pellets or rods are formed by rolling the amalgam between formed rolls and are cut or broken into pre-determined lengths. For example, the rods may be extruded into rods of less than 2 inches in diameter, or less than 1 inch in diameter. In another embodiment, the pellets have a length of less than 2 times their greatest cross sectional dimension. In yet another embodiment, the rods have a length greater than 2 times their greatest cross sectional dimension.

In another embodiment, coal material 202 and solid renewable fuel material 204 are mixed with binder material 218, sufficiently well to allow the mixture to be pressed into briquettes. In one embodiment, the mixture is formed into briquettes of less than 3 inches on the briquette's greatest dimension, or less than 2 inches on the briquette's greatest dimension. In another embodiment, the briquettes have a greatest dimension of less than ½ inch.

These pellets, rods or briquettes will maintain their mechanical integrity during pyrolization and will result in a solid, monolithic, low-volatile, high-carbon, fuel product with chemical and physical properties similar to lump coal. Binder material 218 includes, for example, materials including those listed in reference to the exemplary embodiment shown in FIG. 1. In the alternative embodiment, binder material 218 is, for example, a phenolic like material, of high molecular weight, is unsaturated, and is derived from the highest boiling fraction of recovered pyrolysis oil from oil recovery unit 230, with an initial boiling point above 500° F. In another embodiment, the initial boiling point is above 600° F. and the softening point is greater than 150° F., for example greater than 250° F. In one embodiment, binder material 218 is highly polar and is obtained as the residue of a solvent extraction process against a highly non-polar solvent of a C₁₀ or lower alkane solvent, including hexane, heptane, octane and higher alkanes to decane, or mixtures of the same. In another embodiment, binder material 218 includes the most polar fraction of the highest boiling fraction of the pyrolysis oils from oil recovery unit 230 that are substantially insoluble in heptane at 100° F., and for example, which include a coking value of greater than 60%, or greater than 75%. The extraction process leaves behind the highly polar residue (i.e. the binder material 218), which is useful as a binding agent with substantial unsaturation, oxygenation and cyclic content. In one embodiment, binder material 218 chemically reacts with some or all of the particles from dry blending unit 214 during the pyrolysis process and further strengthens the formed monolithic solid shapes in the form of pellets, rods or briquettes before, during and after the pyrolization process.

Alternatively, the pellets, rods or briquettes are then transferred to dryer 220 and dried at a temperature between 212° F. and 300° F. During drying in dryer 220, water is recovered from the mixture in water recovery unit 222. The pellets, rods or briquettes are then transferred to a first pyrolizer 224 and pyrolized. During pyrolization in first pyrolizer 224, the temperature of the pellets, rods or briquettes is raised to a first temperature, for example, to about 350° F. and mercury is recovered in mercury recovery unit 226. In the alternative embodiment, the pellets, rods or briquettes are then directed to a second pyrolizer 228 and pyrolized. During pyrolization in second pyrolizer 228, the temperature of the pellets, rods or briquettes is raised to a second temperature, for example, to between 800° F. and 1200° F. which reduces the volatile content of the composite fuel product through the evolution of gases that are recovered in oil recovery unit 230 as oil co-product 232. Oil co-product 232 includes coal tar oil. In one embodiment, oil co-product 232 is used directly as fuel, for example as liquid fuel. In another embodiment, oil co-product 232 is further processed into other products including, for example, synthetic crude oil by hydrogenation via hydrocracking and hydrotreating or into coal derived chemicals by means known to those skilled in the art. The originally formed pellets, rods or briquettes maintain their original shapes through pyrolization. Resulting solid char product composite solid fuel 236, of the same shape, with a Hardgrove Grindability Index greater than 30, for example, between 40 and 100, is produced upon cooling in the absence of oxygen in cooling and stabilization unit 234. A composite solid fuel 236 is produced and identifiable in that the individual coal macerals from coal material 202 are clearly identifiable in the pyrolized matrix of composite fuel product 236.

In one embodiment, composite solid fuel 236 is a solid composite non-agglomerating synthetic fuel for use as a substitute power plant fuel. In another embodiment, solid fuel 236 is a solid composite non-agglomerating synthetic fuel for use as a coal substitute metallurgical coal. Composite solid fuel 236 contains a known and uniformly dispersed renewable fuel resource content based on the composition of the feed mixture from dry blending unit 214. For example, composite solid fuel 236 is a monolithic fuel material in the form of pellets, rods or briquettes that is essentially inseparable from coal fuel material 202, while at the same time the maceral structures of coal fuel material 202 remain detectable in composite fuel product 236.

In one embodiment, solid composite fuel 236 is a solid monolithic fuel material formed from the solid pyrolysis products of coal material 202 and solid renewable fuel material 204. In another embodiment, binder material 218 is added to coal material 202 and solid renewable fuel material 204 and formed into a solid shape prior to pyrolysis resulting in a solid monolithic fuel product.

In one embodiment, coal material 202 and solid renewable fuel material 204 are blended into a mixture which may be dried or may be mixed with binder material 218, formed into a solid shape and then dried. The mixture or solid shape is pyrolized in a first pyrolizer and then pyrolized in a second pyrolizer. Resulting solid chars or solid char shapes are cooled to form solid composite fuel 236.

Composite solid fuel 236 exhibits desirable, consistent and repeatable properties including a very low equilibrium moisture content, a precisely controlled volatile content, reduced ash content, a significantly reduced sulfur content, a high fixed carbon content, an improved carbon to hydrogen ratio, a mid-range Hardgrove Grindability Index, and an improved Gross Calorific Value, (GCV), listed in reference to the exemplary embodiment shown in FIG. 2.

In one embodiment, composite solid fuel 236 exhibits an equilibrium moisture content between 0% and 10%. In another embodiment, the equilibrium moisture content is between 0% and 5%. In yet another embodiment, the equilibrium moisture content is between 0% and 2%.

In one embodiment, composite solid fuel 236 exhibits a volatile content between 10% and 30% on a DAF basis. In another embodiment, the volatile content is between 10% and 22% on a DAF basis. In yet another embodiment, the volatile content is between 14% and 22% on a DAF basis.

In one embodiment, composite solid fuel 236 exhibits an ash content between 0% and 10%. In another embodiment, the ash content is between 0% and 5%.

In one embodiment, composite solid fuel 236 exhibits a sulfur content between 0% and 10%. In another embodiment, the sulfur content is between 0% and 5%. In yet another embodiment, the sulfur content is between 0% and 3%. In still another embodiment, the sulfur content is less than 1%.

In one embodiment, composite solid fuel 236 exhibits a fixed carbon content greater than 98%. In another embodiment, the fixed carbon content is between 86% and 98%. In yet another embodiment, the fixed carbon content is between 69% and 86%. In still another embodiment, the fixed carbon content is greater than 69%, or greater than 89%.

In one embodiment, composite solid fuel 236 exhibits a carbon to hydrogen ratio of composite solid fuel between 10 and 30 on a DAF basis. In another embodiment, the carbon to hydrogen ratio is between 10 and 20 on a DAF basis. In yet another embodiment, the carbon to hydrogen ratio is between 15 and 25 on a DAF basis.

In one embodiment, composite solid fuel 236 exhibits a Hardgrove Grindability Index between 30 and 120. In another embodiment, the Hardgrove Grindability Index is between 40 and 100. In yet another embodiment, the Hardgrove Grindability Index is between 80 and 100.

In one embodiment, composite solid fuel 236 exhibits a GCV greater than 10,500 btu/lb. In another embodiment, the GCV is greater than 11,500 btu/lb. In yet another embodiment, the GCV is greater than 12,500 btu/lb.

In one embodiment, composite solid fuel 236 contains greater than 10% solid pyrolysis product from a renewable fuel material, and in another embodiment greater than 20% solid pyrolysis product from a renewable fuel material, and in yet another embodiment, greater than 45% solid pyrolysis product from a renewable fuel material.

In one embodiment, composite solid fuel 236 produces sulfur emissions of less than 1.5 pounds of SO₂ per million BTU.

FIG. 3 is a schematic flow chart of a method for producing a three component carbon mitigating fuel. In the embodiment, a coal material 302 and at least one solid renewable fuel material 304 are selected. Coal material 302 and solid renewable fuel material 304 include, for example, materials listed in reference to the exemplary embodiment shown in FIG. 1. Coal material 302 is directed to and prepared in material preparation unit 306 and solid renewable fuel material 304 is directed to and prepared in material preparation unit 308. Material preparation units 306 and 308 include sizing, analyzing, quantifying and measuring the properties of coal material 302 and solid renewable fuel material 304. Coal material 302 is then directed to metering control unit 310 and solid renewable fuel material 304 is directed to metering control unit 312 where metering control units 310 and 312 feed materials at a rate determined by the moisture and carbon content of feed materials 302 and 304 as measured by material preparation units 306 and 308 respectively, so as to obtain the specified ratio of coal and renewable solid fuel material in the desired composite fuel product 342.

As depicted in FIG. 3, coal material 302 and solid renewable fuel material 304 are blended in dry blending unit 314 sufficiently to produce an essentially uniform mixture of like-sized particles of coal material 302 and renewable solid fuel material 304. The mixture is then directed to mix and pelletize unit 316 which uses heat and pressure to form the mixture into pellets, rods or briquettes. In one embodiment, at least one binder material 318 is added to the mixture to strengthen the subsequent product. In another embodiment, for example, coal material 302 and solid renewable fuel material 304 are mixed with binder material 318, at a sufficiently high sheer rate to further reduce their particle size and produce an essentially homologous amalgam, which is subsequently extruded or rolled into pellets or rods, and in another embodiment, coal material 302 and solid renewable fuel material 304 are mixed with binder material 318, sufficiently well to allow the mixture to be pressed into briquettes.

In one embodiment, the rods may be extruded into rods of less than 2 inches in diameter, or less than 1 inch in diameter. In another embodiment, the pellets have a length of less than 2 times their greatest cross sectional dimension. In yet another embodiment, the rods have a length greater than 2 times their greatest cross sectional dimension.

In another embodiment, coal material 302 and solid renewable fuel material 304 are mixed with at least one binder material, sufficiently well to allow the mixture to be pressed into briquettes. In one embodiment, the mixture is formed into briquettes of less than 3 inches on the briquette's greatest dimension, or less than 2 inches on the briquette's greatest dimension. In another embodiment, the briquettes have a greatest dimension of less than ½ inch.

These pellets, rods or briquettes will maintain their mechanical integrity during pyrolization and will result in solid, monolithic, low-volatile, high-carbon, fuel product 342 of the same shape with chemical and physical properties similar to high-rank lump coal.

In the embodiment depicted in FIG. 3, binder material 318 includes, for example, materials including those listed in reference to the exemplary embodiment shown in FIG. 1 and the alternative embodiment shown in FIG. 2. In one embodiment, binder material 318 includes high molecular weight, unsaturated, phenolic like material, which is derived, for example, from the highest boiling fraction of recovered pyrolysis oil with an initial boiling point above 500° F. In another embodiment, the initial boiling point is above 600° F. and the softening point is greater than 150° F. In one embodiment, binder material 318 is highly polar and is obtained as the residue of a solvent extraction process against C₁₀ or lower alkanes, including hexane, heptane, octane and higher alkanes to decane, or mixtures of the same. In another embodiment, binder material 318 includes the most polar fraction of the highest boiling fraction of the pyrolysis oils that are substantially insoluble in heptane at 100° F., and for example, which include a coking value of greater than 60%, or greater than 75%. The extraction process leaves behind the highly polar residue (i.e. binder material 318), which is useful as a binding agent with substantial unsaturation, oxygenation and cyclic content. Binder material 318 may chemically react with some or all of the particles from dry blending unit 314 during the pyrolysis process and further strengthen the formed monolithic solid shapes in the form of pellets, rods or briquettes before, during and after the pyrolization process.

As depicted in FIG. 3, at least one liquid renewable fuel material 320 is selected as a third fuel material. In one embodiment, liquid renewable fuel material 320 includes material from a class of liquids which will, upon exposure to pyrolizing temperatures, partition into a condensable gaseous phase and a solid phase. The gaseous phase will then be substantially condensed and recovered in oil recovery unit 336, adding to the mass of oil product 338 while the solid phase will remain with and add to composite fuel product 342. Liquid renewable fuel 320 includes, for example, liquid municipal or industrial wastes including petroleum products, that include automotive oil waste, for example, motor oil, transmission fluid, automotive oils and grease. In one embodiment, liquid renewable fuel 320 includes organic solvents, including organic solvent waste that is substantially free of halogen compounds, for example, organic solvents containing less than 1% halogen, including paint thinner which is petroleum naphtha, and the like. In another embodiment, liquid renewable fuel 320 includes trap grease, including trap grease from cooking oils and other waste food based oils such as animal fats and vegetable oil. In yet another embodiment, liquid renewable fuel material 320 includes petroleum processing waste oil, including residual oil from petroleum distillation processes and light and heavy vacuum gas oils from coking. Liquid renewable fuel material 320 is directed to and prepared in material preparation unit 322. Material preparation unit 322 includes analyzing, quantifying and measuring properties of liquid renewable fuel material 320. Liquid renewable fuel material 320 is then directed to metering control unit 324 where metering control unit 324 feeds material at a pre-determined rate, based on the feed rates of coal material 302 from metering control unit 310 and solid renewable fuel 304 from metering control unit 312 and known partitioning ratio of the liquid renewable fuel material into the solid phase of composite solid fuel product 342, so as to obtain the specified ratio of coal and combined renewable solid fuel plus the solid phase of the renewable liquid fuel materials into the monolithic composite solid fuel product 342.

In one embodiment, liquid renewable fuel material 320 is added to binder material 318 to form a reactive binder solution for, at least, the purpose of producing additional pyrolysis oils. In one embodiment, liquid renewable fuel material 320 is added to binder material 318 to form a reactive binder solution for producing both additional pyrolysis oils in oil product 338 and additional solid materials in composite fuel product 342. The renewable liquid fuel material 320 functions with the binder material components from oil recovery unit 336 as a process aid during mixing for the formation of the subsequently formed pellets, rods or briquettes in mix and pelletize unit 316. In one embodiment, the ratio of liquid renewable fuel material 320 to binder material 318 is greater than 1:1, and in another embodiment the ratio is greater than 2:1. In yet another embodiment, liquid renewable fuel 320 is added to binder material 318 and the resulting reactive binder material is then added to the mixture of coal material 302 and solid renewable fuel material 304 in mix and pelletize unit 316.

In the embodiment depicted in FIG. 3, the pellets, rods or briquettes are then directed to dryer 326 and dried at a temperature between 212° F. and 300° F. During drying in dryer 326, water is recovered from the mixture in water recovery unit 328. The pellets, rods or briquettes are then transferred to a first pyrolizer 330 and pyrolized. During pyrolization in first pyrolizer 330, the temperature of the pellets, rods or briquettes is raised to a first temperature for example, to about 350° F. and mercury is recovered in mercury recovery unit 332. In one embodiment, the pellets, rods or briquettes are then transferred to a second pyrolizer 334 and pyrolized at a second temperature. During pyrolization in second pyrolizer 334, the temperature of the pellets, rods or briquettes is raised, for example, to between about 800° F. and 1200° F. and oils are recovered in oil recovery unit 336 as oil product 338. Oil product 338 includes tar oil. In one embodiment, oil product 338 is used directly as fuel, and in another embodiment is further processed into other products including, for example, synthetic crude oil by hydrogenation via hydrocracking and hydrotreating or into coal derived chemicals by means known to those skilled in the art. A resulting solid char is produced after cooling the mixture in cooling and stabilization unit 340.

A composite solid fuel 342 is produced and identifiable in that the individual coal macerals from coal material 302 are clearly identifiable in the pyrolized matrix of composite fuel product 342. In one embodiment, composite solid fuel 342 is a solid composite non-agglomerating synthetic fuel for use as a substitute power plant fuel. In another embodiment, composite solid fuel 342 is a solid composite non-agglomerating synthetic fuel for use as a coal substitute for a metallurgical coal. In both cases, composite solid fuel 342 contains a known and uniformly dispersed renewable fuel resource content based on the composition of the feed mixture. For example, composite solid fuel 342 is a monolithic fuel material in the form of pellets, rods or briquettes that is essentially inseparable from coal fuel material 302, while at the same time the maceral structures of coal fuel material 302 remain detectable in composite fuel product 342.

In one embodiment, solid composite fuel 342 is a solid monolithic fuel material formed from the solid pyrolysis products of coal material 302 and solid renewable fuel material 304. In another embodiment, binder material 318 is added to coal material 302 and solid renewable fuel material 304 and formed into a solid shape prior to pyrolysis resulting in a solid monolithic fuel product.

In one embodiment, coal material 302 and solid renewable fuel material 304 are blended into a mixture which may be dried or may be mixed with binder material 318, formed into a solid shape and then dried. The mixture or solid shape is pyrolized in a first pyrolizer and then pyrolized in a second pyrolizer. Resulting solid chars or solid char shapes are cooled to form solid composite fuel 236.

Composite solid fuel 342 exhibits desirable, consistent and repeatable properties including a very low equilibrium moisture content, a precisely controlled volatile content, reduced ash content, a significantly reduced sulfur content, a high fixed carbon content, an improved carbon to hydrogen ratio, a mid-range Hardgrove Grindability Index, and an improved Gross Calorific Value, (GCV), listed in reference to the exemplary embodiment shown in FIG. 3.

In one embodiment, composite solid fuel 342 exhibits an equilibrium moisture content between 0% and 10%. In another embodiment, the equilibrium moisture content is between 0% and 5%. In yet another embodiment, the equilibrium moisture content is between 0% and 2%.

In one embodiment, composite solid fuel 342 exhibits a volatile content between 10% and 30% on a DAF basis. In another embodiment, the volatile content is between 10% and 22% on a DAF basis. In yet another embodiment, the volatile content is between 14% and 22% on a DAF basis.

In one embodiment, composite solid fuel 342 exhibits an ash content between 0% and 10%. In another embodiment, the ash content is between 0% and 5%.

In one embodiment, composite solid fuel 342 exhibits a sulfur content between 0% and 10%. In another embodiment, the sulfur content is between 0% and 5%. In yet another embodiment, the sulfur content is between 0% and 3%. In still another embodiment, the sulfur content is less than 1%.

In one embodiment, composite solid fuel 342 exhibits a fixed carbon content greater than 98%. In another embodiment, the fixed carbon content is between 86% and 98%. In yet another embodiment, the fixed carbon content is between 69% and 86%. In still another embodiment, the fixed carbon content is greater than 69%, or greater than 89%.

In one embodiment, composite solid fuel 342 exhibits a carbon to hydrogen ratio of composite solid fuel between 10 and 30 on DAF basis. In another embodiment, the carbon to hydrogen ratio is between 10 and 20 on DAF basis. In yet another embodiment, the carbon to hydrogen ratio is between 15 and 25 on DAF basis.

In one embodiment, composite solid fuel 342 exhibits a Hardgrove Grindability Index between 30 and 120. In another embodiment, the Hardgrove Grindability Index is between 40 and 100. In yet another embodiment, the Hardgrove Grindability Index is between 80 and 100.

In one embodiment, composite solid fuel 342 exhibits a GCV greater than 10,500 btu/lb. In another embodiment, the GCV is greater than 11,500 btu/lb. In yet another embodiment, the GCV is greater than 12,500 btu/lb.

In one embodiment, composite solid fuel 342 contains greater than 10% solid pyrolysis product from the combination of char products of the liquid renewable fuel material and the solid renewable fuel material, and in another embodiment greater than 20% solid pyrolysis product from the combination of char products of the liquid renewable fuel material and the solid renewable fuel material, and in yet another embodiment greater than 45% solid pyrolysis product from the combination of char products of the liquid renewable fuel material and the solid a renewable fuel material.

In one embodiment, composite solid fuel 342 produces sulfur emissions of less than 1.5 pounds of SO₂ per million BTU.

Example 1

In one embodiment a method of making a two component carbon mitigating fuel is provided as shown in FIG. 1.

The two starting fuel components are coal from the classes of bituminous, sub-bituminous or lignite and a selected solid renewable fuel. The solid renewable fuel includes woody biomass, Bagase (from sugar cane processing), miscanthus, switch grass or other terrestrial plant materials. The solid renewable fuel generally contains moisture of between 5% and 50%, ash in the range of 2% to 6%, volatile matter in the range of 40% to 90% on a dry ash-free basis, fixed carbon content of between 10% and 70% on a dry ash-free basis, and a sulfur content of less than 3% on a dry ash-free basis, and/or aquatic plant material. The solid renewable fuel material may include aquatic plant material including algae or diatoms, either whole or with their oil component substantially depleted, having similar moisture and ash content and volatile matter, fixed carbon and sulfur contents on a dry ash-free basis. All or part of the renewable content may be substituted with carbon containing solid municipal or industrial waste material. The solid waste material includes wood, paper, coated paper, plastic which does not contain halogen compounds in excess of 1%, dry sewage sludge, reclaimed plastics, paper, composite materials, shredded automobile tires and the like. When the material includes dry sewage sludge, the ash content of the sludge is sufficiently low for the desired fuel application. For example, the ash content is less than 20%, or less than 10%. The mixture contains similar amounts of moisture, ash, volatile matter, fixed carbon and sulfur as the specified biomass. The selected materials are then prepared and pyrolized as follows:

In a first preparation step, the materials are reduced in size by methods known to those skilled in the art to less than 1 inch, for example less than ½ inch, or to less than ¼ inch. The materials may also be reduced to less than 0.1 inch. The materials are chemically analyzed and quantified to determine their moisture and carbon content. The mixture is then dry blended to form a substantially homologous mixture of similar sized particles such that the mixture, when pyrolized, will yield the desired properties. In the next step, the mixture is dried at between 212° F. and 300° F. for a sufficient period of time to reduce the water content to less than 2%, or less than 1%, in the drying section of the equipment train. After drying, the material is transferred to the pyrolysis process which may be of a single stage or may have multiple stages, for further control of regulated pollutants. Process methods known to those skilled in the art as described in Encoal Project Final Report DOE/MC/27339-5798 are used, the steps of which are described in this example.

The mixed and dried material is introduced into a first pyrolizer. The first pyrolizer raises the material temperature to about 350° F. forcing the evaporation of mercury from the coal component of the mixture for collection, before the material is transferred to a second pyrolizer. The second pyrolizer raises the temperature of the mixture to about 800° F. to 1200° F. in the absence of oxygen to cause “destructive distillation” of volatile hydrocarbons from all the organic materials present which are collected as an “oil product” or “tar oil” which is a mixture of coal-oils and pyrolysis oils from other renewable fuel sources, including post consumer waste materials like plastics, which may be used directly as fuel or processed further by hydrogenation to produce a synthetic crude oil or by distillation and separation methods known by those skilled in the art to produce industrial chemicals. These oils may also be further processed into other products including synthetic crude oil and other chemicals. The resulting solid char product after cooling and, if required, stabilization, is essentially equivalent to low-sulfur/low-volatile bituminous coal with sulfur emissions of less than 1.5 pounds of SO₂ per million BTU. The resulting solid char has a moisture content of less than 3%, reduced volatile content of between 14% and 22% on a dry ash-free basis, and an ash content of less than 10% or less than 5%. The resulting solid char has a sulfur content of less than 3%, or less than 1% on a dry ash-free basis, a highly concentrated fixed carbon content in the range of 78% to 86% on a dry ash-free basis, and a Carbon to Hydrogen ratio between 15 and 20 on a dry ash-free basis. The resulting solid char has a Hardgrove Grindability Index between 30 and 120, for example, between 40 and 100, or between 80 and 100, and a known and uniform renewable resource content based on the composition of the feed mixture, for use as a coal-substitute power plant fuel and with known renewable fuel content.

For the purpose of reducing dust in shipping and handling, the resultant char is formed into pellets, rods or briquettes with addition of a binder. The binder may include a sugar syrup or starch solution. Tar oil produced during pyrolysis may be substituted for all or part of the binder. Components of the tar oil that have an initial boiling point above 500° F., and contain substantial amounts of waxy and/or phenolic compounds may be substituted for all or part of the binder as described above in the description of FIG. 1. Additionally, components having an initial, boiling point above 600° F., and containing substantial amounts of waxy and/or phenolic compounds may also be substituted for all or part of the binder also as described above in the description of FIG. 1. The composite solid fuel is identifiable in that the individual pyrolized coal macerals are clearly identifiable in the composite fuel matrix.

Example 2

In another embodiment, a method of making a two component carbon mitigating fuel is provided as shown in FIG. 2.

The two starting fuel components are coal from the classes of bituminous, sub-bituminous or lignite and a selected solid renewable fuel. All or part of the solid renewable fuel may include woody biomass, Bagase (from sugar cane processing), miscanthus, switch grass or other terrestrial plant materials. The solid renewable fuel generally contains moisture of between 5% and 50%, ash in the range of 2% to 6%, volatile matter in the range of 40% to 90% on a dry ash-free basis, fixed carbon content of between 10% and 70% on a dry ash-free basis, and a sulfur content of less than 3% on a dry ash-free basis. All or part of the solid renewable fuel material may be substituted with aquatic plant material, including algae or diatoms, either whole or with their oil component substantially depleted, having similar moisture and ash content and volatile matter, fixed carbon and sulfur contents on a dry ash-free basis. All or part of the solid renewable content may be substituted with carbon containing solid municipal or industrial waste material. The solid waste material includes wood, paper, coated paper, plastic which does not contain halogen compounds in excess of 1% by dry weight, dry sewage sludge, reclaimed plastics, paper, composite materials, shredded automobile tires and the like. When the material includes dry sewage sludge, the ash content of the sludge is sufficiently low for the desired fuel application. For example, the ash content is less than 20%, or less than 10%. The mixture contains similar amounts of moisture, ash, volatile matter, fixed carbon and sulfur as the specified biomass. The selected materials are then prepared and pyrolized as follows:

In a first preparation step, the materials are reduced in size by methods known to those skilled in the art to less than 1 inch, for example less than ½ inch, or to less than ¼ inch. The materials may also be reduced to less than 0.1 inch. The materials are chemically analyzed and quantified to determine their moisture and carbon content. The mixture is then dry blended to form a substantially homologous mixture of like sized particles. For example, the particles are mixed with a binder and formed into briquettes which retain their distinct shape through drying and pyrolysis. The particle mixture of coal material and renewable solid fuel material are mixed with the binder material at high mechanical intensity using machinery appropriate for the task, including twin-screw extruders with co-rotating screws, Banbury Mixers, Ball Mill, Paint Mill, Roll Mill and the like. The mixing causes further particle size reduction, to form a near homogeneous amalgam of the two materials. The binder material may be added during high-sheer mixing or the binder material may be subsequently mixed with the amalgam after the high sheer mixing step. The binder is added to the mixture to strengthen the subsequent amalgam which is extruded into pellets or rods or pressed into briquettes. Alternately, the rods or pellets may be formed by rolling the amalgam between profiled rolls. These pellets, rods or briquettes have the physical strength to be handled with bulk processing equipment and will maintain their mechanical integrity during pyrolization to result in a solid, monolithic, low-volatile, high-carbon, fuel product with chemical and physical properties similar to lump coal. The binder material is a phenolic like material, of a high molecular weight, is unsaturated, and is derived from the highest boiling fraction of the collected pyrolysis oil. The initial boiling point is above 500° F., or above 600° F., and the softening point of greater than 150° F. The binder material is highly polar and is obtained as the residue of solvent extraction process against highly non-polar alkane solvents including hexane, heptane, octane, and higher alkanes up to decane or mixtures of same. The extraction process leaves the highly polar residue (i.e. the binder material) behind, which is useful as a binding agent with substantial unsaturation, oxygenation and cyclic content because of the affinity of the polar hydrocarbon content with the bound particles of the coal and the renewable solid fuel materials and the tendency of the binder material to convert to carbon rather than gas during the pyrolization process. These binders have a coking value of greater than 60%, or greater than 75%.

In the next step, the resultant pellets, rods or briquettes are dried at between 212° F. and 300° F. for a sufficient period of time to substantially remove all moisture. The drying reduces the water content to less than 2%, or less than 1%, in the drying section of the equipment train which conveys the formed pellets, rods or briquettes through the heating section by means known to those skilled in the art, including rotory kiln, vibratory conveyor and the like. After drying, the material is transferred to the pyrolysis process which may be of a single stage or may have multiple stages, for further control of temperature profile, regulated pollutants, using process equipment and methods known to those skilled in the art as noted in Example 1. The steps are further described in this example.

The dried pellets, rods or briquettes are introduced into a first pyrolizer. The first pyrolizer raises the material to a first temperature of about 350° F. This forces the evaporation of mercury from the coal component of the mixture for collection prior to raising the temperature of the material to the pyrolysis temperature of about 800° F. to 1200° F. The material is transferred to a second pyrolizer. This section raises the temperature of the mixture to about 800° F. to 1200° F. in the absence of oxygen causing “destructive distillation” of volatile hydrocarbons from all the organic materials present which are collected as an “oil product.” The oil product includes “tar oil” which is a mixture of coal-oils and pyrolysis oils from other renewable fuel sources, including post consumer waste materials like plastics. These oils may be used directly as fuel or processed further by hydrogenation via hydrocracking and hydrotreating as used in heavy oil upgrading by conventional refineries into a synthetic crude oil or by distillation and separation methods, known by those skilled in the art, into industrial chemicals. The yield of condensable gases from the second pyrolizer is about 10% to 20% of the mass of material coming from the mix and pelletize unit and depends on the amount and type of the renewable fuel material supplied to the process.

For example, if the renewable fuel material includes post consumer plastics, the fraction of post consumer plastics can be expected to be converted into approximately 80% condensable oils. The amount expected to be converted into condensable oils (i.e. 80%) is added to the oil product. The majority of the balance of pyrolysis products, less the amount lost to gas, is added to the mass of the composite fuel product. For example, if the plastic material comprises 50% of the charge from the dry blending unit, then the oil product yield from the plastic fraction of the charge is 40% of the total oil yield, (50%×80%). Therefore, a balance of 10% of the composite fuel product yield comes from the plastic charge, (50%×20%), less any pyrolysis gases from the plastic charge that escaped the process.

The resulting solid composite fuel product, after cooling and, if required, stabilization, is essentially equivalent to low-sulfur/low-volatile bituminous coal and with known renewable fuel content with SO₂ emissions of less than 1.5 pounds per million BTU. The resulting solid char has an equilibrium moisture content of less than 3%, reduced volatile content of between 14% and 22% on a dry ash-free basis, and an ash content of less than 10% or less than 5%. The resulting solid char has a sulfur content of less than 3%, or less than 1% on a dry ash-free basis, a highly concentrated fixed carbon content in the range of 78% to 86% on a dry ash-free basis, and a Carbon to Hydrogen ratio between 15 and 20 on a dry ash-free basis. The resulting solid char has a Hardgrove Grindability Index between 30 and 120, for example, between 40 and 100, or between 80 and 100, and individual coal macerals are identifiable in the pyrolized composite fuel matrix. The fuel contains a known and uniform renewable resource content based on the composition of the feed mixture, for use as a coal-substitute power plant fuel.

Example 3

In a further embodiment, a three component carbon mitigating fuel is provided as shown in FIG. 3.

The two starting fuel components are coal from the classes of bituminous, sub-bituminous or lignite and a selected solid renewable fuel. All or part of the solid renewable fuel may include woody biomass, Bagase (from sugar cane processing), miscanthus, switch grass or other terrestrial plant materials. For example, the solid renewable fuel generally contains moisture of between 5% and 50%, ash in the range of 2% to 6%, volatile matter in the range of 40% to 90% on a dry ash-free basis, fixed carbon content of between 10% and 70% on a dry ash-free basis, and a sulfur content of less than 3% on a dry ash-free basis, and/or aquatic plant material. All or part of the solid renewable fuel material may include aquatic plant material including algae or diatoms, either whole or with their oil component substantially depleted, having similar moisture and ash content and volatile matter, fixed carbon and sulfur contents on a dry ash-free basis. All or part of the renewable content may be substituted with carbon containing solid municipal or industrial waste material. The solid waste material includes wood, paper, coated paper, and plastic which does not contain halogen compounds in excess of 1% by dry weight, dry sewage sludge, reclaimed plastics, paper, composite materials, shredded automobile tires and the like. When the material includes dry sewage sludge, the ash content of the sludge is sufficiently low for the desired fuel application, for example, less than 20% or less than 10%. The mixture contains similar amounts of moisture, ash, volatile matter, fixed carbon and sulfur as the specified biomass. The selected materials are then prepared and pyrolized as follows:

In a first preparation step, the coal material and renewable fuel material are reduced in size by methods known to those skilled in the art to less than 1 inch, for example less than ½ inch, or to less than ¼ inch. The materials may also be reduced to less than 0.1 inch. The materials are chemically analyzed and quantified to determine their moisture and carbon content. The mixture is then dry blended to form a substantially homologous mixture of like sized particles in a dry blending unit, for example, in a tumble blender, V-blender or others known to one skilled in the art.

A third fuel component is a renewable liquid fuel material selected from a class of liquids which will, upon exposure to pyrolizing temperatures, partition into a condensable gaseous phase and a solid phase, such that the gaseous phase, then will be substantially condensed and recovered in oil recovery unit, adding to the mass of oil product while the solid phase will remain with, and add to, the composite fuel product. The renewable liquid fuel material is comprised substantially of liquid municipal or industrial waste materials including used or waste petroleum products, including automotive motor oil or residue from petroleum processing, organic solvents that do not contain halogens in excess of 1% by weight, trap grease, used cooking oils, and the like. The renewable liquid fuel material is blended with binder material, the preparation of which is as described in Example 2, to form a near homogeneous mixture using methods known to those skilled in the art, including high sheer mixing techniques, for example, homogenation to form unbreakable emulsions which do not readily separate into the component materials. A reactive binder solution formed in this manner is added to the material from the dry blending unit, so that the material binds the particles together when pressed into briquettes or when extruded into pellets or rods and will undergo destructive distillation as described in Example 2. Additional composite fuel product and additional pyrolysis oil product are produced in amounts proportional to (percent condensable volatile organic vapor from the renewable solid fuel material)×(fraction of the renewable solid fuel material)+(percent condensable volatile organic vapor from the renewable liquid fuel material)×(fraction of the renewable liquid fuel material). The balance of the mass of renewable fuel materials less any pyrolysis gases that escape the process, add to composite fuel product.

The binder material functions as a process aid during high-sheer mixing and forming operations of pelletizing, rod forming or briquetting. The binder material strengthens the subsequently formed pellets, rods or briquettes so as to retain their formed shape through the subsequent processes of drying, pyrolizing and shipping. The proportions of the third fuel component to reactive binder material are greater than 1:1, or greater than 2:1. The portion of binder material which is not composed of renewable liquid fuel material, is a phenolic like material, of a high molecular weight, is highly unsaturated, and is derived from the highest boiling fraction of the collected pyrolysis oils from the oil recovery unit, as described above in Example 2. The initial boiling point is above 500° F., or above 600° F., and the softening point is greater than 150° F. The binder material is highly polar and is obtained as the residue of a solvent extraction of the high-boiling fraction against solvents of C₁₀ or lower alkanes, including hexane, heptane, octane and higher alkanes to decane, or mixtures of the same. The extraction process leaves behind the highly polar residue (i.e. the phenolic portion of the binder material), which is useful as a binding agent with substantial unsaturation, oxygenation and cyclic content. Binder material may chemically react with some or all of the particles from the dry blending unit, while being processed in the mix and pelletize unit, during the pyrolysis process and further strengthen the formed monolithic solid shapes in the form of pellets, rods or briquettes before, during and after the pyrolization process, because of the affinity of the polar hydrocarbon content with the bound particles and the tendency of the binder material to convert to carbon rather than gas during the pyrolization process as described in Example 2.

The materials are then mixed with binder material at high mechanical intensity using machinery appropriate for the task, including twin-screw extruders, Banbury Mixers, Ball Mill, Roll Mill and the like, which are incorporated into mix and pelletize unit. The mixing causes further particle size reduction, to form a near homogeneous amalgam of the three materials. The binder material may be added during high-sheer mixing or the binder material may be subsequently mixed with the amalgam after the high sheer mixing step. The binder material is added to the mixture to strengthen the subsequent amalgam which is extruded or rolled into pellets or rods or pressed into briquettes. These pellets, rods or briquettes have the physical strength to be handled with bulk processing equipment and will maintain their mechanical integrity during pyrolization to result in a solid, monolithic, low-volatile, high-carbon, fuel product with chemical and physical properties similar to lump coal and with known renewable fuel content.

In the next step, the resultant pellets, rods or briquettes are dried at between 212° F. and 300° F. for a sufficient period of time to remove substantially all moisture. The drying reduces the water content to less than 2%, or less than 1%, in the dryer. After drying, the material is transferred to the pyrolysis process which may be of a single stage or may have multiple stages, for further control of regulated pollutants. The steps are further described in this example.

The dried pellets, rods or briquettes are introduced into a first pyrolizer that raises the material to a first temperature of about 350° F. This forces the evaporation of mercury from the coal component for collection prior to raising the temperature in the second pyrolizer. The material is transferred to a second pyrolizer that raises the temperature of the pellets, rods or briquettes to about 800° F. to 1200° F. in the absence of oxygen to cause “destructive distillation” of volatile hydrocarbons from the organic materials present. The hydrocarbons are collected as an oil product through condensation in the oil recovery unit. The oil product includes primarily “tar oil” which is a mixture of coal-oils and pyrolysis oils from the renewable solid and liquid fuel materials. The pyrolysis oil product may be used directly as fuel or processed further by hydrogenation processes including hydrocracking and hydrotreating into a synthetic crude oil by conventional refinery means or by distillation and separation methods, known by those skilled in the art, into coal based industrial chemicals. The yield of condensable gases from the second pyrolizer is dependent on the amount and type of both renewable solid fuel material and renewable liquid fuel material supplied to the process and the partitioning coefficients of each.

For example, if renewable fuel material includes post woody biomass, forest biomass or miscanthus, the fraction of woody biomass can be expected to be converted into approximately 30% condensable oils. The amount expected to be converted into condensable oils (i.e. 30%) is added to the oil product. The balance of the pyrolysis products, less the amount lost to gas, is added to the mass of the composite fuel product. For example, if the woody biomass comprises 50% of the feed stock sent to the dry blending unit, then the oil product from the woody biomass is 15% of the total oil product yield, (50%×30%). Therefore, a balance of 35% of the composite fuel product yield comes from the renewable solid fuel material (woody biomass), (50%×70%), less any pyrolysis gases from the woody biomass which escaped the process.

A further example of the process includes the addition of a liquid renewable fuel material to increase the yield of both the oil product and the composite fuel product. Condensable organic vapors are produced during pyrolization and carburization of the residual carbon components of the renewable liquid fuel material. Taking the above example, in which 50% of the dry blended feedstock from the mix and pelletize unit was composed of renewable solid fuel material, the replacement of a portion of the binder material, which if of a phenolic type, evolves very little condensable gases, but instead tends to carbonize, is replaced with a renewable liquid fuel material, which generates condensable organic vapors, and thereby additional oil product is generated. For example, in a mixture from the mix and pelletize unit containing 20% by weight of the binder material which is composed of 66% renewable liquid fuel material which in the case of this example is taken to be trap grease that converts almost completely to condensable organic vapors upon pyrolization, then an additional 13% (66%×20%) oil product is recovered from the process, while composite fuel product is reduced by 7% (34%×20%). Under certain economic circumstances this is a very desirable outcome since the value synthetic crude oil produced from the oil product is about 8 times the value of the composite fuel product.

The resulting composite fuel product, after cooling and, if required, stabilization against autoignition, is essentially equivalent to low-sulfur/low-volatile bituminous coal but with known renewable content and with SO₂ emissions of less than 1.5 pounds per million BTU. The resulting solid char has an equilibrium moisture content of less than 3%, a reduced volatile content of between 14% and 22% on a dry ash-free basis, and an ash content of less than 10% or less than 5%. The resulting solid char has a sulfur content of less than 3% or less than 1% on a dry ash-free basis, a highly concentrated fixed carbon content in the range of 78% to 86% on a dry ash-free basis, and a Carbon to Hydrogen ratio between 15 and 20 on a dry ash-free basis. The resulting solid char has a Hardgrove Grindability Index between 30 and 120, for example, between 40 and 100 or between 80 and 100, and individual coal macerals are identifiable in the pyrolized composite fuel matrix. The fuel contains a known and uniform renewable resource content based on the composition of the feed mixture, for use as a coal-substitute power plant fuel with known renewable content.

Although the compositions and methods are described in reference to a coal-fired power plant, the compositions and methods described herein may also be suitable for use in other industrial and residential systems to facilitate mitigating undesirable emissions including, for example, industrial heating systems and residential heating systems.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

1.-19. (canceled)
 20. A method of making a solid composite fuel, the method comprising: preparing a coal material and at least one solid renewable fuel material; blending the coal material and the at least one solid renewable fuel material into a mixture; drying the mixture; pyrolyzing the mixture in at least one pyrolyzer; and cooling resulting solid chars to form a solid composite fuel.
 21. The method according to claim 20 wherein preparing the coal material and the at least one solid renewable fuel material comprises at least one of sizing, analyzing and quantifying the coal material and the at least one solid renewable fuel material.
 22. The method according to claim 20 further comprising a step of forming the resulting solid chars into at least one of pellets, rods and briquettes.
 23. The method according to claim 20 further comprising recovering at least one of mercury, a tar oil product, and a liquid condensate from evolved pyrolysis gases from the at least one pyrolyzer.
 24. The method according to claim 23 further comprising at least one of utilizing the recovered tar oil as fuel and processing the recovered tar oil.
 25. The method according to claim 20 further comprising adding at least one binder material to the coal material and the at least one solid renewable fuel material in one of prior to, during and after the blending of the coal component and the at least one solid renewable fuel material.
 26. The method according to claim 25 further comprising preparing at least one liquid renewable fuel material and blending the at least one liquid renewable fuel material with the at least one binder material.
 27. The method according to claim 20 further comprising selecting the coal material from the class of lignite, sub-bituminous or bituminous coal; and selecting the solid renewable material from at least one of: (a) terrestrial plant biomass such as forest or cane plants or grasses; (b) petroleum coke; (c) aquatic plant biomass such as algae, micro algae and diatoms; (d) waste synthetic solid materials containing less than 1% halogen; and (e) combinations thereof.
 28. The method according to claim 20 wherein the preparing step further comprises sizing the coal material and the solid renewable material to like-sized particles; and analyzing at least one of the moisture content and the carbon content of each of the coal material and the solid renewable material.
 29. The method according to claim 28 wherein the blending step further comprises separately metering the coal material and the solid renewable material in response to the analyzed moisture content or the analyzed carbon content, or both of the coal material and the solid renewable material.
 30. The method according to claim 20 wherein the mixture has a dry weight fraction of coal material of greater than 50%.
 31. The method according to claim 20 wherein the drying step further comprises drying the mixture at a temperature of between 212 degrees Fahrenheit and 300 degrees Fahrenheit for a time sufficient to achieve a moisture content of less than 2% moisture prior to introduction into the at least one pyrolyzer.
 32. The method according to claim 20 wherein the pyrolyzing step further comprises pyrolyzing at a temperature between 800 degrees Fahrenheit and 1,200 degrees Fahrenheit.
 33. The method according to claim 20 wherein the pyrolyzing step further comprises at least two sequential pyrolyzing steps.
 34. The method according to claim 25 wherein the binder includes at least one of: a blend of sugar syrup and starch; unsaturated or oxygenated or cyclic hydrocarbons such as phenolic resins; and a portion of tar oil product condensed from pyrolysis gases and having an atmospheric boiling point above 500 degrees Fahrenheit.
 35. The method according to claim 34 wherein the tar oil portion of the binder material is the residue resulting from the solvent extraction of the condensed pyrolysis liquids having an atmospheric boiling point of greater than 500 degrees Fahrenheit, where the extraction is carried out against an alkane solvent of less than 10 carbons, against cyclo-pentane or against cyclo-hexane or a mixture thereof at a temperature of less than 250 degrees Fahrenheit.
 36. The method according to claim 35 wherein of the binder material is the residue resulting from the solvent extraction of the condensed pyrolysis liquids having an atmospheric boiling point of greater than 600 degrees Fahrenheit.
 37. The method according to claim 22 wherein the pyrolyzing step occurs prior to the forming step.
 38. The method according to claim 21 further comprising a step of forming the mixture into at least one of pellets, rods and briquettes step, and wherein the forming step occurs prior to the pyrolyzing step.
 39. The method according to claim 38 further comprising adding at least one binder material to the coal material and the at least one solid renewable fuel material prior to the pyrolyzing step, the binder material including a portion of tar oil product condensed from pyrolysis gases and having an atmospheric boiling point above 500 degrees Fahrenheit.
 40. The method according to claim 39 further comprising metering a liquid renewable fuel material into the mixture in addition to the coal material and the at least one solid renewable fuel material.
 41. The method according to claim 40 wherein a portion of the liquid renewable fuel material comprises a tar oil product recovered from a pyrolysis step.
 42. A product for use as a metallurgical coal product made by the method of claim 20 and having the following properties: a GCV in excess of 12,500 BTU per pound; an equilibrium moisture of less than 5% by weight; and a volatile matter content of less than 15% by weight.
 43. A product for use as a CO₂ mitigating power plant fuel product made by the method of claim 20 and having the following properties: a GCV in excess of 12,500 BTU per pound; an equilibrium moisture of less than 5% by weight; and a volatile matter content of less than 25% by weight. 